Straw Hat's Sweetheart
by miyaaabi
Summary: Sierra is a sassy sword-wielding pirate and the latest addition to the straw-hats. As she gets accustomed to the crew and their adventures continue, she takes an interest in a certain green Marimo. (Starts in Water Seven ARC with lots of relapsing arcs and some original ones) ZORO X OC , LUNA
1. Chapter 1 - Sierra

**A/N : New story! Please leave reviews if you enjoy, they will motivate me to write more!**

"Marines!" The sharpshooter yelled as he put down his binoculars and ran to warn the rest of the crew.

"How many?" Nami responded, reaching over to grab her Clima Tact.

"Two warships!"

Luffy, Zoro, and Sanji all smirked and made their way towards the deck - each excited to get some action, it had been a while since they had any battles, after all.

"I call the one on the right," Luffy yelled and the captain swung his rubber arm until it latched onto the sail of the largest warship - towards the right of the small enemy fleet. Before anyone could protest, he flung himself off the Going Merry. The rest of the crew prepared themselves for battle on the ship, as grapple hooks were flung around and Marines were soon swarming them.

These Marine ambushes, when they occurred, followed a routine. First off, they would fire some rounds of cannons. Then, as they sailed closer, all the weak new Marines would be sent to attack first, as the cowardly ones who might have stood a chance watched from the safety of their ship. And finally, once they see the ultimate defeat looming, the retreat bell would sound and those who could move, would make their way back to any boat they could.

Within the Straw Hats, a routine was also followed. As soon as the ships were close enough, Luffy would fling himself off onto the biggest and most exciting-looking one. Zoro would follow his captain's aggressive suit, as he would ambush the first batch of Marines that set foot onto the Merry, before searching out the strongest-looking enemy. Usopp, Chopper, and Nami would normally cower behind the ever-protective Sanji and use their long-distance spells to assist the fight as best as they could. Robin would back up Zoro, and use her abilities to fight off any loose cannons that were still being fired.

Soon enough, the retreat bell was sounding. All the capable Marines on the ship tried their best to crawl towards the rescue boats that were being sent to them.

"Alright, when Luffy gets back we are getting out of here before reinforcements arrive," Nami stated as she straightened her dress.

"Speak of the devil," Sanji spoke and pointed towards the only Marine ship that wasn't sailing quickly away in retreat. Their captain was standing on the side of the railings, waving his arms back and forth in earnest. When he saw he had gotten their attention, Luffy motioned for them to come his way.

"He obviously wants us to meet him. Maybe he found something on the ship?" Usopp commented, trying to strain his eyes to see behind Luffy.

Nami sighed, she really didn't want to stay here any longer than needed, however, there was the possibility that the ship held treasure. With this in her mind, she got the crew sailing towards Luffy as fast as the Merry could go.

The crew walked around the Marine ship, looking for their reckless captain.

"Guys! Down here!"

They followed the sound of Luffy's voice, and it led the crew down some stairs and into what looked to be a dark, deep cellar. Luffy appeared through the dark, clutching something shiny in his arms. Before the crew could ask what he had found, Nami had swooped in and stolen the items from Luffy's grasp, leaning in to examine it with glee.

"That's…" Chopper gasped. "Pure gold?"

Luffy nodded," That's right, and there's heaps of it all over the place in here."

Nami was breathing heavily and almost looked like she would faint from happiness. "Sanji-kun, can you feel around for a light switch?"

The blond cook did as he was told, and after a few moments he flipped a switch, and the room filled with light. It was larger than the crew expected, and they all looked on in awe as in the back of the room, stacked up high, was a large mountain of gold and various other shiny yellow artifacts.

"Wow.."

Chopper's strangled whisper resembled the entire crew's reaction. Nami was in heaven as she was overwhelmed by such a sight.

A rough and hoarse cough interrupted the silence that had been brewing. Luffy moved in the direction of the sound and discovered that behind the mountain of gold, there was another staircase. The excited teen rushed down them and found himself glad that the light from upstairs transferred down. He paused in his adventurous movements as the rest of the crew followed and stood behind him.

In front of them, tied up and bloodied, was a motionless girl. Her hair was dark brown and flowed onto the ground beside her kneeling legs. Her eyes were half-lidded and she could barely put together the figures that stood in front of her.

"What's your name?" was all she heard.

As her consciousness faded away, she managed to mumble out, "Sierra."

Chopper had immediately begun untying the now unconscious girl. The reindeer was solely focused on helping this badly injured girl recover.

"Wait, Chopper - we can't just take this girl with us. What if she's a marine? Or dangerous somehow?" Usopp asked, questioning his doctor's motives.

Chopper only shook his head.

"Let's look at the facts," Robin spoke calmly. "She is clearly not a Marine, they wouldn't treat one of their own this way. Being tied up down here means that she's an enemy - the natural response to that is that she is a pirate or bounty hunter."

Nami nodded. "Being down here with all this treasure - they probably took it from a pirate crew that she was a part of."

Usopp sighed, "that doesn't mean that she isn't dangerous - in fact being a pirate probably makes her more dangerous."

Sanji glared at the sharpshooter very hard. "There is no way we are going to leave such a gorgeous young lady here to die."

Zoro rolled his eyes at the annoying cook, before heading over to stand behind Luffy. "It's your call, captain," he spoke, not even bothering to make eye contact with the girl. "Do we take her or leave her?"

Luffy barely even took a moment to decide. "She doesn't seem too dangerous to me, so we'll take her."

And that was the end of it.

" _Maya!" Sierra found herself yelling out, unable to watch as her sister fought against multiple marines. She gripped her wrists together, feeling the cold blade tease against her throat as she stood there, helplessly. Tears filled her eyes as her sister's cries got weaker._

 _"How could you do this, Riku? To your own crew?" Sierra cried out. Her eyes focused on the traitor who held the blade to her throat._

Sierra's eyes creaked open and she took a moment to adjust to the bright lighting of the room. She weakly glanced around, the room was small, and the walls looked a little bit run-down but it was obviously an infirmary of sorts. She pushed herself up a tad, wincing as pain ran through her entire body.

"Oh! You're finally awake."

Sierra watched with wide eyes as a tiny reindeer waddled over.

"How do you feel?" Chopper asked.

Her mouth dropped. "Y-you just spoke?" she asked, her voice coming out as a creaky whisper.

"Drink this," Chopper said and handed her a potion before hopping onto the edge of the bed. "I'm Chopper. A reindeer who ate the human-human devil fruit."

Sierra managed a weak nod before she downed the liquid.

"Where am I?" she asked, beginning to become a little more aware of her surroundings.

Chopper smiled, glad to see his patient recovering. "You're on board a pirate ship," he explained. "We rescued you from some Marines, you were being held captive - do you remember how it happened?"

Sierra frowned, "on a pirate ship?" she repeated, trying to piece together the rest of the events after the brief flashback. Suddenly, she shot up, ignoring the pain. "Was there anyone else with me? Another young girl - someone who looked like me but older?"

Chopper's brow creased, "no. It was only you."

Sierra tried to force herself to be brave. But it was hard.

"I should introduce you to the rest of the crew," Chopper said and made his way out of the room. Sierra tried to not let her thoughts wander, and thankfully a few moments later the door opened once more. This time, there were a lot more people following him inside. She watched as they all crowded around the bed, looking curiously down at her.

"Everyone - this is Sierra," Chopper said. "And Sierra, these are the Straw Hats. This is our captain, Luffy," Chopper began, pointing to Luffy, and then to Zoro. "This is Zoro, Nami, Usopp, Sanji, and Robin." Sierra nodded, trying to remember face to name.

"My beautiful Sierra, I hope you are feeling better," Sanji spoke as he knelt beside her bed and reached out to grasp her hand in his. "I will make you some food as soon as possible. Anything, in particular, you would like?"

Nami stood in front of Sanji and slapped the back of his head. "Before that, we have to make sure this girl is not a threat to us. Tell us why you were being held captive by the Marines and who you are," the red-head demanded.

Sierra froze. She didn't want to remember. But these people... they were pirates.

"And if I don't tell you?" she asked.

Nami stepped over Zoro, who was leaning against the wall lazily. She reached down to pick up one of his swords, unsheathed it and held it against Sierra's throat. The brunette gasped quietly but regained her composure quickly.

"My sister and I joined a pirate crew a year ago called the Akuma pirates," she began, her mind roaming back to where it started. " It was great at first, everything we wanted. So much freedom and power. About five months ago, a new member joined us. Riku. He quickly climbed up the ranks, and was soon the unofficial first mate. Then, a few days ago he changed completely. His personality became dark. We all thought it was just a phase. But then, yesterday we were attacked by marines. We were ready to fight for our lives - but then Riku started attacking his own crew. He killed all of us off, one by one. He held a knife to my throat as I was forced to watch my sister fight for her life. Then, I guess he must have knocked me out because that's all I remember," Sierra's eyes were dry. "He betrayed us," her voice didn't quiver.

Everyone was silent.

"There. Happy? You know everything."

Zoro watched her, curious. This girl had just been through a devastating ordeal, and yet she wasn't showing any emotion. It was respectable, but strange. Even he would probably show emotion if that were him.


	2. Chapter 2 - The Crew

_**A/N ; please review if you are enjoying!**_

It had been two days since the Straw Hats agreed to save Sierra. The crew was currently heading towards the next island on the log-pose, where they agreed to safely take her. The trip was taking quite awhile, and Luffy and Usopp were getting unusually anxious since they had been at sea for a very long time. Sierra, on the other hand, was finding herself growing increasingly fond of the young reindeer who had saved her life. He was such a strange creature, yet so adorable and intelligent.

"Chopper-kun, do you need any help preparing anything?" Sierra asked, following the reindeer into the infirmary.

Chopper paused for a moment, before shaking his head. "I don't think so. But have you taken your pain killer medicine today?"

Sierra nodded. The teen was feeling a lot better, and the only noticeable injures were some dark bruises and a broken arm that was being held up in a white print sling. Her strength was slowly returning too, much to her delight.

"By the way, Sierra, why don't you get to know some of the other crew members?" Chopper asked curiously. "I really appreciate you helping out, but I know everyone else is interested to get to know you at least a little."

Sierra nodded, "that's a good idea. I'm just a little shy I suppose. But you guys did save my life, so I suppose I should at least try."

"I recommend starting with someone friendly, and open like-" Chopper spun around to face her, but she had already left.

Sierra walked around the deck of the Going Merry. It was a great day for sailing. On days like this, her sister and her had many traditions. Sometimes they would fish, duel, or just talk about the good old days living in East Blue before everything was so complicated. The rest of the crew was loitering about up on deck, with Luffy and Usopp checking out some new weapon the sniper had made. Nami and Robin were sunbathing, Sanji providing them with cocktails and sunscreen. Sierra turned to her right and spotted Zoro leaning against the side of the ship, sharpening his swords. She gulped before moving towards him. She slid down onto the ground next to him and forced a smile.

"Hey," she said. "It's Zoro, right?"

The swordsman scoffed. "Yeah," he replied. Obviously uninterested in conversation, but Sierra didn't give easily.

"You're a swordsman?" She continued, trying to get a better response from the man.

Zoro looked up from his swords for a moment and studied her face. The cuts on her face were healing, but still visible. Her long hair was tied up in a high ponytail and she wore a tight black dress - probably one of Nami's or Robin's. Zoro still didn't know why she was talking to him, or what she wanted.

"Yep," he said. He didn't trust her, and it wasn't surprising as none of them besides Chopper had much contact with her the past couple days.

"Do you use all three swords?" she prodded, eager to learn about his swordsmanship.

Zoro was getting a little annoyed with all the questions. Was she trying to learn his weakness so she could expose the crew?

"Yeah. What's it to you?" he retorted, probably being a little harsh with his tone. Sierra was also getting annoyed. This guy was being so unnecessarily rude, she was just trying to make conversation.

"Geez, someone's cranky." She rolled her eyes and got up. Maybe he wasn't the best choice to get to know. As she glanced around the deck, Sanji finally noticed her. He skipped down the stairs and took her hand in his, planting a soft kiss on it.

"It's nice to see you, Sierra-chan," he spoke with a soothing voice. "Would you like something to eat? Possibly a drink?"

Sierra just giggled. Guys like this were totally clueless and fawn over any woman they spy. "A drink sounds lovely," she replied in an equally soft tone. The blond cook smiled and made his way into the kitchen. Sierra decided she may as well follow, at least he wanted to talk to her. She sat at one of the bar stools, noticing that Nami had also relocated there.

"Hey Sierra," the Navigator smiled. "How's the dress feel?"

Sierra smiled back. "I love it!"

Meanwhile, Sanji mixed together a delicious orange cocktail for her. Making sure to pour it into a fancy wide-rimmed glass before handing it to her.

"Thank you Sanji-kun," she said as she took it. After taking a sip she smiled again - it was amazing. "It's so good!"

Both Nami and Sanji grinned.

"Sanji's the best chef I know," Nami stated.

Sanji swooned in this compliment, his eyes turning into little pink hearts. "Thank you Nami-Swan!"

Sierra felt she already had a pretty good idea what type of guy Sanji is, however, Nami was intriguing. She could have such a harsh side - as displayed when she threatened Sierra. But there seemed to be a sweet side to her as well, like when she offered the dress to Sierra. Or maybe she just felt bad after hearing the sob-story. Either way, Sierra was slowly taking a liking to the orange-haired Navigator. Sanji was charming too, although she had a feeling he might be a bit overwhelming sometimes

"What are you making for lunch today?" Nami asked from behind Sierra.

Sanji thought about it for a moment, "I was thinking various types of sandwiches." Nami seemed pleased by this.

"Want to join us sunbathing?" Nami spoke again, directing the question to Sierra, who nodded happily. "Come and try one of my bikinis on."

Zoro's eyes opened, and he strained them to avoid the direct sunlight. Not a moment later, a door opened and he heard a giggle from beside him. He turned and groaned. The Ero-Cook was standing beside him, his eyes peeled in front of Zoro, making the swordsman turn around. Sierra was following Nami as they exited the ladies room. She was borrowing one of the Navigator's bikinis, it had a poka-dot print and extenuated the woman's curves perfectly. Her breasts were not as large as those of Nami's or Robin's, but they were more shapely and perky. Zoro's eye lowered to a tattoo printed on Sierra's left thigh. It was in the shape of a crescent moon, with a sword going through it. It was unique and interesting, he liked it.

He noticed Robin was no longer sunbathing. She was instead sitting on her own. Which was not overly weird in itself, but he and Nami had been noticing Robin had been acting weird for awhile now. It was odd, to say the least. However, Robin was still somewhat new to the crew so Zoro suspected it might be one of her quirks.

"Guys!" Usopp's voice rang out. "I see the next island!"

Luffy rushed out of the kitchen, where he had been stealing food, and hurried to glance out the front of the deck.

"It's so big, look at the design!" Usopp continued.

Everyone, including Robin, headed to the front to look out towards their next adventure.

It was an extremely large island. In fact, it looked more like a massive ship than an island. There were many houses that were build on an incline, leading up to the largest waterfall that any of the Straw Hats had ever seen. On the outer circle of the island, there were many open gates that allowed water to flow out; giving the impression that the island had a lot of water inside it's borders.

"It looks amazing!" Luffy yelled, earning himself a light punch in the back of the head from Nami because he was so unnecessarily loud. Although the volume was unneeded, Luffy's comment remained correct in all of the Straw Hat's minds.

Robin was the only one who did not wear some form of a smile. Her mouth was closed in a tight-lipped frown, and her fingers were clenched around the railing of the Merry so hard her knuckles were turning white.

The only person who noticed the archeologist's silent reaction was Sierra. And she was both concerned and intrigued.


End file.
